1. Field of the Invention
This invention relates to the field of container handling, for example in bottling plants, and in particular to an improvement of handling systems for plastic bottles, including a method and apparatus for adding a quantity of ballast to the bottles for stable transport on horizontal conveyors.
2. Prior Art
In a conventional bottling system, empty bottles are supplied on pallets wherein levels of bottles are stacked on one another with interleaved panels providing a supporting surface for the bottles on each level or rank. A depalletizer receives the pallet and raises the pallet until the topmost level or rank of bottles is coplanar with a receiving platform. The rank of bottles is then urged laterally onto the receiving platform. The receiving platform leads to a funnel-like path wherein successive decreases in width force the bottles into single file, from which the bottles proceed one after another through continuously operating processing steps. This funnel-like section serves to accumulate the bottles because each rank from the depalletizer requires a certain time to be converted from an X-Y array of bottles to a single file, and theoretically, the next rank is supplied just as the previous rank is exhausted.
The bottles in the single file are then carried by a conveyor typically having one or more endless loops of conveyor belt, horizontally attached link plates, or rollers, which define a moving horizontal platform for supporting the bottles while advancing the bottles to the next processing station. Each bottle simply rests on a horizontal surface which is moved to advance the bottle. The bottles move through stations typically including the depalletizer and funnel arrangement as described, a bottle washer or rinser, where the bottles are inverted and a fluid is sprayed in from below and then allowed to drain, and a filler and capper. The filler and capper has a carousel with a plurality of filling positions at which an empty bottle can be received, filled and finally capped, while moving along a conveying path.
The bottling system preferably runs continuously. For maximum production it is necessary to avoid both stoppages of the line and gaps in the single file progression of bottles. In addition to the lost production caused by gaps in the line, the bottles to some extent support one another upright as they are moved along the conveyor. Where gaps occur, the bottles leading and trailing the gap lack support from adjacent bottles and more easily fall over. When a bottle falls over, the entire line may become jammed.
The depalletizer which unloads ranks of bottles necessarily operates intermittently. Therefore, it is not possible to avoid all gaps in the progression of bottles. Similarly, various occurrences along the path of the bottles may result in gaps opening up. Typically, one or more workers are required to watch the line and to clear jams.
The general nature of bottling plants is well known and well developed. In recent years, however, plastic containers have come into use. The plastic containers are thin but durable, and light in weight, which qualities have obvious advantages in reduction of shipping weight, ability to use lighter production equipment and the like. However, the bottles are so lightweight as to be unstable when carried on a horizontal conveyor surface. In order to avoid jamming of bottling lines when running plastic bottles, the lines are run substantially more slowly than a comparable line running glass bottles, which are heavier and therefore more stable. Even at slower rates of throughput, the plastic bottles tend to fall over much more frequently than do glass bottles, and more workers are needed to correct recurrent jamming and resume proper operation of the line.
Plastic bottles are used for a wide variety of products. A typical lightweight plastic bottle is made of polyethylene terephthalate (PET). Standard bottle capacities, for example for beverage containers are 16 ounce, 20 ounce, 1 liter and 2 liter. Of course other sizes are also possible and in standard use for various products. In recent years, technical advances have reduced the weight of plastic bottles by as much as 30%. Whereas a glass bottle in a beverage container size might weigh 6 ounces, the comparable plastic bottle may weigh only 0.25 ounce. The bottles are generally relatively tall and thus are easily knocked over by uneven conveyor passages, impacts, or even by a breeze in the bottling plant.
Plastic bottles can be made with an excess of plastic at the bottom, which helps to preclude fallover. A "petaloid" form of bottle has a scalloped bottom with radially oriented folds which increase the rigidity of the bottle at the bottom and also provide additional weight at the bottom due to the additional material at the fold. Another form of bottle is the "champagne" type, which has an inward dome in the bottom. Some bottles are supplied with an outer reinforcing cup that is bonded to the outside of the bottle at the bottom. The reinforcing cup is generally made of less expensive plastic than PET, is opaque rather than clear, and defines a bottom weight that makes the empty bottle more stable when placed on its bottom. The reinforcing cup, however, conceals the content at the bottom, requires additional manufacturing steps and renders the bottle unacceptable for recycling into new PET material. The bottom cap can add as much as 15% to the weight of the bottle. Recycling operations typically cut off and discard the entire bottom of cupped bottles in order to recycle the PET top.
Another method for dealing with problems encountered in handling plastic bottles is to vary the nature of the conveyor. According to one method, the plastic bottles are not carried on horizontal support surfaces, but rather by a structure having rails or flanges that face inwardly near the neck of the bottle. The bottles are provided with a circumferential bead or flange at the neck, that rests on the conveyor rails to support the bottle. In an embodiment known as an Airveyor, the bottles are supported entirely by the rails, and blasts of air are used to propel the bottles along the conveyor path. While such systems are useful, it would be desirable to provide a substantially jam-proof arrangement that does not require added bottle material, processing requirements and/or conveyor structure.
In order to enable an increase in production speed in processes such as bottling plants which require the handling of plastic bottles, it would be desirable to render the bottles more stable without increasing the cost of bottle production and materials. It would also be desirable to provide a means to render the bottle stable temporarily, i.e., when empty, which does not increase the weight of the bottle. It would be most desirable to enable plastic bottles to run dependably on simple horizontal conveyor surfaces, in the same manner as a glass bottle.